JP2005125690A - Method of forming inkjet image, image forming apparatus, and method of forming proof image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming an inkjet image capable of accurately controlling a density of an image, an image forming apparatus, and a method of forming a proof image using the same. <P>SOLUTION: In this method of forming an inkjet image, an image is formed by a first ink including a colorant and the image is corrected by a second ink including a white pigment. In the method, the first ink and the second ink are not to be mixed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inkjet image forming method, an image forming apparatus, and a proof image forming method using the same, and more particularly to an ink jet image forming method, an image forming apparatus, and a proof image forming method using the same, which can accurately control image density.

  In recent years, the inkjet recording method can easily and inexpensively create images, and thus has been applied to various printing fields such as photographs, various printing, proofing, marking, and special printing such as color filters. In particular, an image recording device that discharges and controls fine dots, ink that has improved color reproduction range, durability, and ejection suitability, ink absorbency, coloring material color development, surface gloss, etc. are dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper. The image quality improvement of today's inkjet recording system is achieved only when all of the image recording apparatus, ink, and special paper are available.

  In recent years, color images are frequently formed based on digital data, but the ink jet recording method has a large individual difference between recording devices, and individual differences can be achieved by software such as a color management system. Actions to eliminate have been taken. However, in the field of proofing, remote proofing has been studied in earnest, and there is no individual difference between recording apparatuses, and more precise color adjustment from the low density part to the high density part is required.

  For example, first printing means for printing dots with colored ink on a recording material, second printing means for printing dots with white or colorless ink on the recording material, and printing with colored ink Inkjet printer comprising: first control means for controlling the size of the dots to be printed; and second control means for controlling so that the dots of the white or colorless ink are superimposed on the dots of the colored ink Is disclosed (for example, see Patent Document 1). This technique prints gray dots by printing dots having a lower density than dots of the minimum size black ink, thereby improving the gradation of the low density region.

  The invention described in the publication is a technique aiming to create a color having a reduced density with white ink, thereby enhancing the gradation reproduction capability of only the low density portion, and is intended for the low density intended by the present invention. There is no concept of correcting the density from the high density part to the high density part, and there is no concept of correcting after the image is formed once.

  Further, the image data consisting only of colored area data formed by the first developer that is colored is extracted by the shaggy extraction means for extracting the shaggy present in the image data, and the shaggy extraction means. An image processing apparatus comprising: a covering data forming unit that forms covering data for covering the corners of the shaggy with a second developer with respect to the shaggy. For example, see Patent Document 2.) As a result, it is possible to reproduce a high-definition image by printing with white toner on the shaggy jagged edges that occur on the diagonal edge of the printed image, eliminating the sharp edges of the shaggy and smoothing the shaggy. Is stated. However, nothing is said about the adjustment of the concentration intended by the present invention.

  On the other hand, a technique for reproducing an image by superimposing white ink and non-white ink is disclosed (see, for example, Patent Document 3). However, this publication aims to improve ink bleeding, and this application The purpose is different.

  Further, in an ink jet recording method for recording an image by ejecting ink droplets onto a recording medium, an image reading device is provided to read an image of the recording medium itself, and processing of the recording medium and printing on the recording medium accordingly. An ink jet recording method is disclosed (see Patent Document 4, for example). It is stated that this makes it possible to make the influence of the image on the back surface that occurs when performing double-sided copying or the like, or the stain on the recording medium inconspicuous. The purpose of this publication is to erase unnecessary images, and there is no concept of density correction intended by the present invention.

Therefore, there is a demand for a technique that does not cause individual differences between ink jet recording apparatuses and achieves more strict color adjustment from a low density portion to a high density portion.
Japanese Patent Laid-Open No. 11-58707 JP 2001-341352 A JP 2003-145745 A JP 2003-182054 A

  The present invention has been made in view of the above problems, and an object of the present invention relates to an inkjet image forming method, an image forming apparatus, and a proof image forming method using the same, and an inkjet image forming method capable of accurately controlling image density, An object of the present invention is to provide an image forming apparatus and a proof image forming method using the same.

The above object of the present invention is achieved by the following configurations.
(Claim 1)
In an inkjet image forming method in which an image is formed with a first ink containing a color material and then the image is corrected with a second ink containing a white pigment, the first ink and the second ink are not mixed. An ink jet image forming method.
(Claim 2)
The inkjet image forming method according to claim 1, wherein the transmittance of the second ink image portion is 80% or less.
(Claim 3)
The inkjet image forming method according to claim 1, wherein the second ink is an actinic ray curable white ink.
(Claim 4)
It has a first inkjet head that ejects at least one kind of yellow, magenta, cyan, and black ink, and a second inkjet head that ejects white ink, and the second inkjet head is an image by the first inkjet head. An inkjet image forming apparatus arranged to form an image after formation.
(Claim 5)
The inkjet image forming method according to claim 1, wherein the apparatus according to claim 4 is used.
(Claim 6)
A proof image forming method using the ink jet image forming method according to claim 1.

  According to the present invention, it is possible to provide an ink jet image forming method, an image forming apparatus, and a proof image forming method using the same, in which image density can be accurately controlled.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  As a result of intensive studies in view of the above problems, the present inventors have formed an image with a first ink containing a color material, and then corrected the image with a second ink containing a white pigment. In the method, by using an ink characterized in that the first ink and the second ink are not mixed, a white ink is formed when an image is formed with a colored ink and then measured to measure the density. It was found that the concentration can be controlled and corrected by overshooting. Further, it has been found that the use of actinic radiation curable ink for the white ink is less likely to bleed and the density can be accurately controlled, and the present invention has been achieved.

  Hereinafter, the present invention will be described in detail.

  In the ink set of the present invention, the second ink is a white ink containing a white pigment, and is not mixed with a first ink containing a color material (hereinafter also referred to as a color ink).

  The white pigment used in the white ink according to the present invention is not particularly limited as long as it makes the ink composition white. Usually, white pigments used in this field can be used. It is preferable to use a white pigment, an organic white pigment, or white hollow polymer fine particles.

  Examples of inorganic white pigments include alkaline earth metal sulfates such as barium sulfate, alkaline earth metal carbonates such as calcium carbonate, silicas such as finely divided silicic acid and synthetic silicates, calcium silicate, alumina, alumina Hydrates, titanium oxide, zinc oxide, talc, clay and the like can be mentioned. In the present invention, titanium oxide is particularly preferable from the viewpoints of concealability, colorability, and dispersed particle size. In particular, with regard to the concealing property, the transmittance of the second ink image portion is preferably 80% or less, and one preferred embodiment is a white ink having a transmittance of 20% or less, and another preferred embodiment is as follows. The transmittance is 20 to 90%, preferably 50 to 85%, more preferably 60 to 80%. By using inks having different transmittances, it is possible to finely adjust inks having a transmittance of 20% or less in the case of significant correction, and inks having a high transmittance if the correction is slight. .

  Examples of the organic white pigment include organic compound salts disclosed in JP-A No. 11-129613 and alkylene bismelamine derivatives disclosed in JP-A Nos. 11-14365 and 2001-234093.

  Specific examples of commercially available white pigments include Shigenox OWP, Shigenox OWPL, Shigenox FWP, Shigenox FWG, Shigenox UL, and Shigenox U (all trade names manufactured by Hackol Chemical Co., Ltd.).

  Examples of the white hollow polymer fine particles include fine particles showing thermoplasticity substantially made of an organic polymer as disclosed in US Pat. No. 4,089,800. White pigments may be used alone or in combination.

  For dispersing the white pigment, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. It is also possible to add a dispersant when dispersing the white pigment. A polymer dispersant is preferably used as the dispersant.

  Examples of the polymer dispersant include Solsperse series manufactured by Zeneca. Moreover, it is also possible to use a synergist according to various white pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the white pigment. The dispersion medium is a solvent or a polymerizable compound. In the case of an ink having curability by actinic ray irradiation, which will be described later, it is preferably solventless because it reacts and cures immediately after ink landing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The dispersion preferably has an average particle size of 0.1 to 1.0 μm, and the maximum particle size is 0.3 to 10 μm, preferably 0.3 to 3 μm. Set selection, dispersion conditions, and filtration conditions. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink concealment, and curing sensitivity can be maintained.

  The content of the white pigment can be appropriately changed in order to control the transmittance, but it is preferably contained in the range of 1 to 50% by mass, preferably 2 to 30% by mass of the entire ink composition. If the content is less than this, the concealing property cannot be obtained, and if it is more than this, the light emitting property by the ink jet is deteriorated, which causes clogging and the like.

  The ink set of the present invention is composed of color ink and white ink. After the color ink is ejected and a color image is formed so that the color ink and the white ink are not mixed, the white ink is ejected with a time difference. In addition, it is preferable to overlay a white ink on the color image. The time difference may be appropriately determined by measuring the time during which the color ink dries on the recording material and does not mix even when the white ink is overlaid. In addition, each color ink contains a polymerizable compound and a photopolymerization initiator together with a colorant. After being ejected onto the recording material, it is cured by irradiation with an actinic ray, and further contains a polymerizable compound and a photopolymerization initiator. Then, it is also a preferable aspect to superimpose white inks that are cured with actinic rays.

  Hereinafter, the polymerizable compound used in the present invention will be described.

  As a 1st form of the polymeric compound used for this invention, an oxetane compound and an epoxy compound or a vinyl ether compound are mentioned.

  The proportion of the oxetane compound in the entire ink composition is preferably 65 to 95% by mass. Japanese Patent Application Laid-Open No. 2001-220526 discloses an energy ray curable ink composition for an inkjet recording system containing an oxetane compound, and the ratio of the oxetane compound to the entire ink composition is 65 to 95% by mass. Is preferred.

  The oxetane compound that can be used in the present invention means a compound having an oxetane ring. For example, known oxetane compounds such as those described in JP-A Nos. 2001-220526 and 2001-310937 are used. I can do it.

  In the oxetane compound used in the present invention, when a compound having 5 or more oxetane rings is used, the viscosity of the produced ink becomes high, which makes it difficult to handle and increases the glass transition temperature of the ink. The cured product is not sufficiently sticky. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.

  Hereinafter, although the specific example of the compound which has an oxetane ring used for this invention is demonstrated, this invention is not limited to these.

  An example of the compound having one oxetane ring is a compound represented by the following general formula (1).

In the general formula (1), R ¹ is a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group or other alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, or an aryl group. , Furyl group or thienyl group. R ² is an alkyl group having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 2-methyl- C2-C6 alkenyl group such as 2-propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group, etc. A group having an aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethylcarbonyl group, a propylcarbonyl group, and a butylcarbonyl group, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethoxycarbonyl group, a propoxycarbonyl group, and a butoxycarbonyl group; Alkoxycarbonyl group, ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, pentylcarbamoyl Is N- alkylcarbamoyl group having a carbon number of 2-6 and the like. As the oxetane compound used in the present invention, it is particularly preferable to use a compound having one oxetane ring because the resulting composition has excellent tackiness, low viscosity and excellent workability.

  An example of a compound having two oxetane rings includes a compound represented by the following general formula (2).

In the general formula (2), R ¹ is the same group as that in the general formula (1). R ³ is, for example, a linear or branched alkylene group such as an ethylene group, a propylene group or a butylene group, a linear or branched poly (alkyleneoxy) such as a poly (ethyleneoxy) group or a poly (propyleneoxy) group. ) Group, propenylene group, methylpropenylene group, butenylene group or other linear or branched unsaturated hydrocarbon group, alkylene group containing carbonyl group or carbonyl group, alkylene group containing carboxyl group, alkylene containing carbamoyl group Group.

Moreover, as R < ³ >, the polyvalent group selected from the group shown by the following general formula (3), (4) and (5) can also be mentioned.

In the general formula (3), R ⁴ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a methoxy group, an ethoxy group, a propoxy group, or a butoxy group. An alkoxy group having 1 to 4 carbon atoms, a halogen atom such as a chlorine atom or a bromine atom, a nitro group, a cyano group, a mercapto group, a lower alkyl carboxyl group, a carboxyl group, or a carbamoyl group.

In the general formula (4), R ⁵ represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO ₂ , C (CF ₃ ) ₂ , or C (CH ₃ ) ₂ .

In General formula (5), R < ⁶ > is a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, or an aryl group. n is an integer of 0-2000. R ⁷ is a methyl group, an ethyl group, a propyl group, a butyl group having 1 to 4 carbon atoms, or an aryl group. R ⁷ may further include a group selected from the group represented by the following general formula (6).

In General formula (6), R < ⁸ > is a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, or an aryl group. m is an integer of 0-100.

  Specific examples of the compound having two oxetane rings include the following compounds.

Illustrative compound 1 is a compound in which R ¹ is an ethyl group and R ³ is a carbonyl group in general formula (2). Exemplary compound 2 is a compound in which, in the general formula (2), R ¹ is an ethyl group, R ³ is the general formula (5), R ⁶ and R ⁷ are methyl groups, and n is 1.

Among the compounds having two oxetane rings, preferred examples other than the above compounds include compounds represented by the following general formula (7). In general formula (7), R ¹ has the same meaning as R ¹ in the general formula (1).

  An example of a compound having 3 to 4 oxetane rings is a compound represented by the following general formula (8).

In the general formula (8), R ¹ is the same meaning as R ¹ in the general formula (1). As R ⁹ , for example, a branched alkylene group having 1 to 12 carbon atoms such as groups represented by the following A to C, a branched poly (alkyleneoxy) group such as a group represented by the following D, or the following E And branched polysiloxy groups such as those shown. j is 3 or 4.

In the above A, R ¹⁰ is a lower alkyl group such as a methyl group, an ethyl group or a propyl group. Moreover, in said D, p is an integer of 1-10.

  Illustrative compound 3 is an example of a compound having 3 to 4 oxetane rings.

  Furthermore, examples of the compound having 1 to 4 oxetane rings other than those described above include compounds represented by the following general formula (9).

In the general formula (9), R ⁸ has the same meaning as R ⁸ in the general formula (6). R ¹¹ is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group or a trialkylsilyl group, and r is 1 to 4.

  Preferable specific examples of the oxetane compound used in the present invention include the following compounds.

  The production method of each compound having an oxetane ring described above is not particularly limited, and may be a conventionally known method, for example, Pattisson (DB Pattison, J. Am. Chem. Soc., 3455, 79). (1957)) discloses a method for synthesizing an oxetane ring from a diol. In addition to these, compounds having 1 to 4 oxetane rings having a high molecular weight of about 1000 to 5000 are also included. Examples of these specific compounds include the following compounds.

  Next, the epoxy compound used in the present invention will be described.

  As the epoxy compound, for example, any known epoxy compound disclosed in JP-A-2001-55507, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-310938 can be used.

  Preferred as the aromatic epoxide is diglycidyl ether or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, for example, bisphenol A Alternatively, diglycidyl ether or polyglycidyl ether of an alkylene oxide adduct thereof, hydrogenated bisphenol A or diglycidyl ether or polyglycidyl ether of an alkylene oxide adduct thereof, and a novolac type epoxy resin can be used. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peroxide. Oxide or cyclopentene oxide-containing compounds are preferred.

  Preferred examples of the aliphatic epoxide include diglycidyl ether or polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof, and typical examples thereof include diglycidyl ether of ethylene glycol and diglycidyl of propylene glycol. Polyglycidyl ethers of polyhydric alcohols such as diglycidyl ethers of alkylene glycols such as ether or 1,6-hexanediol, diglycidyl ethers of glycerin or alkylene oxide adducts thereof, polyethylene glycols or alkylene oxides thereof Polyglycerides such as diglycidyl ether of adducts, polypropylene glycol or diglycidyl ether of alkylene oxide adducts thereof Diglycidyl ether of glycol, and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable. In the present invention, one of the epoxides may be used alone with the oxetane compound, but two or more may be used in appropriate combination.

  Next, the vinyl ether compound used in the present invention will be described.

  As the vinyl ether compound used in the present invention, any known vinyl ether compound can be used, for example, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether. Di- or trivinyl ether compounds such as vinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, trimethylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl Bi Ether, cyclohexanedimethanol monovinyl ether, n- propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether -O- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, divinyl ether compounds or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone together with the oxetane compound, but two or more thereof may be used in appropriate combination.

  Examples of the second form of the polymerizable compound used in the present invention include pyrrole and substituted pyrrole, aniline and substituted aniline, thiophene and substituted thiophene.

  Examples of the substituted pyrrole include N-alkylpyrroles such as N-methylpyrrole and N-ethylpyrrole, N-arylpyrroles such as N-phenylpyrrole, 2-nitrophenylpyrrole, 3-methylpyrrole, 3-ethylpyrrole, Examples of substituted anilines such as 3-chloropyrrole, 3,4-dimethylpyrrole, and 3,4-dichloropyrrole include N-methylaniline, N-ethylaniline, N-dimethylaniline, N-diethylaniline, chloraniline, di Examples of substituted thiophenes such as chloroaniline, chloro-N-methylaniline, chloro-N-dimethylaniline, dichloro-N-acetylaniline, phenylenediamine, etc. include 3-methylthiophene, 3-ethylthiophene, 3-chlorothiophene, 3, 4-dimethylthiophene, 3,4-dichloro Thiophene, 2,2'-bithiophene and the like.

  The specific example of the radically polymerizable compound in this invention is given.

<Examples of acrylates>
Examples of monofunctional alkyl acrylates: methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate Cyclohexyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, benzyl acrylate.

  Examples of monofunctional hydroxy acrylates: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3-chloropropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxy-3-allyloxypropyl Acrylate, 2-acryloyloxyethyl-2-hydroxypropyl phthalate.

  Examples of monofunctional halogen-containing acrylates: 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 1H-hexafluoroisopropyl acrylate, 1H, 1H, 5H-octafluoropentyl acrylate 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate, 2,6-dibromo-4-butylphenyl acrylate, 2,4,6-tribromophenoxyethyl acrylate, 2,4,6-tribromophenol 3EO addition Acrylate.

  Examples of monofunctional ether-containing acrylates: 2-methoxyethyl acrylate, 1,3-butylene glycol methyl ether acrylate, butoxyethyl acrylate, methoxytriethylene glycol acrylate, methoxypolyethylene glycol # 400 acrylate, methoxydipropylene glycol acrylate, methoxy Tripropylene glycol acrylate, methoxy polypropylene glycol acrylate, ethoxydiethylene glycol acrylate, 2-ethylhexyl carbitol acrylate, tetrahydrofurfuryl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxy polyethylene glycol acrylate, cresyl polyethylene glycol acrylate , P- nonyl phenoxyethyl acrylate, p- nonylphenoxy polyethylene glycol acrylate, glycidyl acrylate.

  Examples of monofunctional carboxyl-containing acrylates: β-carboxyethyl acrylate, succinic acid monoacryloyloxyethyl ester, ω-carboxypolycaprolactone monoacrylate, 2-acryloyloxyethyl hydrogen phthalate, 2-acryloyloxypropyl hydrogen phthalate, 2-acryloyl Oxypropyl hexahydrohydrogen phthalate, 2-acryloyloxypropyl tetrahydrohydrogen phthalate.

  Examples of other monofunctional acrylates: N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropyl acrylate, morpholinoethyl acrylate, trimethylsiloxyethyl acrylate, diphenyl-2-acryloyloxyethyl phosphate, 2-acryloyloxyethyl Acid phosphate, caprolactone-modified-2-acryloyloxyethyl acid phosphate.

  Examples of bifunctional acrylates: 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 200 diacrylate, polyethylene glycol # 300 diacrylate, polyethylene glycol # 400 diacrylate, polyethylene glycol # 600 diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, tetrapropylene glycol diacrylate, polypropylene glycol # 400 diacrylate, polypropylene glycol # 700 diacrylate , Neopentyl glycol diacrylate, neopent Glycol PO (propylene oxide) modified diacrylate, hydroxypivalic acid neopentyl glycol ester diacrylate, caprolactone adduct diacrylate of hydroxypivalic acid neopentyl glycol ester, 1,6-hexanediol bis (2-hydroxy-3-acryloyloxy) Propyl) ether, 1,9-nonanediol diacrylate, pentaerythritol diacrylate, pentaerythritol diacrylate monostearate, pentaerythritol diacrylate monobenzoate, bisphenol A diacrylate, EO (ethylene oxide) modified bisphenol A diacrylate, PO Modified bisphenol A diacrylate, hydrogenated bisphenol A diacrylate, EO modified hydrogenation Sphenol A diacrylate, PO modified hydrogenated bisphenol A diacrylate, bisphenol F diacrylate, EO modified bisphenol F diacrylate, PO modified bisphenol F diacrylate, EO modified tetrabromobisphenol A diacrylate, tricyclodecane dimethylol diacrylate , Isocyanuric acid EO-modified diacrylate.

  Examples of trifunctional acrylates: glycerin PO modified triacrylate, trimethylolpropane triacrylate, trimethylolpropane EO modified triacrylate, trimethylolpropane PO modified triacrylate, isocyanuric acid EO modified triacrylate, isocyanuric acid EO modified ε-caprolactone modified Triacrylate, 1,3,5-triacryloylhexahydro-s-triazine, pentaerythritol triacrylate, dipentaerythritol triacrylate tripropionate.

  Examples of tetrafunctional or higher acrylates: pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate monopropionate, dipentaerythritol hexaacrylate, tetramethylolmethane tetraacrylate, oligoester tetraacrylate, tris (acryloyloxy) phosphate.

<Examples of methacrylates>
Examples of monofunctional alkyl methacrylates: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, stearyl methacrylate, isobornyl methacrylate Cyclohexyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, benzyl methacrylate.

  Examples of monofunctional hydroxy methacrylates: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxy-3-chloropropyl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, 2-hydroxy-3-allyloxypropyl Methacrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate.

  Examples of monofunctional halogen-containing methacrylates: 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1H-hexafluoroisopropyl methacrylate, 1H, 1H, 5H-octafluoropentyl methacrylate 1H, 1H, 2H, 2H-heptadecafluorodecyl methacrylate, 2,6-dibromo-4-butylphenyl methacrylate, 2,4,6-tribromophenoxyethyl methacrylate, 2,4,6-tribromophenol 3EO addition Methacrylate.

  Examples of monofunctional ether-containing methacrylates: 2-methoxyethyl methacrylate, 1,3-butylene glycol methyl ether methacrylate, butoxyethyl methacrylate, methoxytriethylene glycol methacrylate, methoxypolyethylene glycol # 400 methacrylate, methoxydipropylene glycol methacrylate, methoxy Tripropylene glycol methacrylate, methoxy polypropylene glycol methacrylate, ethoxydiethylene glycol methacrylate, 2-ethylhexyl carbitol methacrylate, tetrahydrofurfuryl methacrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol methacrylate, phenoxy polyethylene glycol methacrylate, cresyl poly Ethylene glycol methacrylate, p- nonyl phenoxyethyl methacrylate, p- nonylphenoxy polyethylene glycol methacrylate, glycidyl methacrylate.

  Examples of monofunctional carboxyl-containing methacrylates: β-carboxyethyl methacrylate, succinic acid monomethacryloyloxyethyl ester, ω-carboxypolycaprolactone monomethacrylate, 2-methacryloyloxyethyl hydrogen phthalate, 2-methacryloyloxypropyl hydrogen phthalate, 2-methacryloyl Oxypropyl hexahydrohydrogen phthalate, 2-methacryloyloxypropyl tetrahydrohydrogen phthalate.

  Examples of other monofunctional methacrylates: N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl methacrylate, morpholinoethyl methacrylate, trimethylsiloxyethyl methacrylate, diphenyl-2-methacryloyloxyethyl phosphate, 2-methacryloyloxyethyl Acid phosphate, caprolactone-modified-2-methacryloyloxyethyl acid phosphate.

  Examples of bifunctional methacrylates: 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol # 200 dimethacrylate, polyethylene glycol # 300 dimethacrylate, polyethylene glycol # 400 dimethacrylate, polyethylene glycol # 600 dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, tetrapropylene glycol dimethacrylate, polypropylene glycol # 400 dimethacrylate, polypropylene glycol # 700 dimethacrylate Neopentylglyco Dimethacrylate, neopentyl glycol PO modified dimethacrylate, hydroxypivalic acid neopentyl glycol ester dimethacrylate, caprolactone adduct dimethacrylate of hydroxypivalic acid neopentyl glycol ester, 1,6-hexanediol bis (2-hydroxy-3-methacryloyl) Oxypropyl) ether, 1,9-nonanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol dimethacrylate monostearate, pentaerythritol dimethacrylate monobenzoate, bisphenol A dimethacrylate, EO modified bisphenol A dimethacrylate, PO modified bisphenol A Dimethacrylate, hydrogenated bisphenol A dimethacrylate, EO Hydrogenated bisphenol A dimethacrylate, PO modified hydrogenated bisphenol A dimethacrylate, bisphenol F dimethacrylate, EO modified bisphenol F dimethacrylate, PO modified bisphenol F dimethacrylate, EO modified tetrabromobisphenol A dimethacrylate, tricyclodecane dimethylol Dimethacrylate, isocyanuric acid EO-modified dimethacrylate.

  Examples of trifunctional methacrylates: glycerin PO modified trimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane EO modified trimethacrylate, trimethylolpropane PO modified trimethacrylate, isocyanuric acid EO modified trimethacrylate, isocyanuric acid EO modified ε-caprolactone modified Trimethacrylate, 1,3,5-trimethacryloyl hexahydro-s-triazine, pentaerythritol trimethacrylate, dipentaerythritol trimethacrylate tripropionate.

  Examples of tetrafunctional or higher functional methacrylates: pentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate monopropionate, dipentaerythritol hexamethacrylate, tetramethylolmethane tetramethacrylate, oligoester tetramethacrylate, tris (methacryloyloxy) phosphate.

  Examples of arylates: allyl glycidyl ether, diallyl phthalate, triallyl trimellitate, isocyanuric acid triarylate.

  Examples of acid amides: acrylamide, N-methylolacrylamide, diacetoneacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N-isopropylacrylamide, acryloylmorpholine, methacrylamide, N-methylolmethacrylamide, diacetone Methacrylamide, N, N-dimethylmethacrylamide, N, N-diethylmethacrylamide, N-isopropylmethacrylamide, methacryloylmorpholine.

<Examples of styrenes>
Styrene, p-hydroxystyrene, p-chlorostyrene, p-bromostyrene, p-methylstyrene, p-methoxystyrene, pt-butoxystyrene, pt-butoxycarbonylstyrene, pt-butoxycarbonyloxystyrene 2,4-diphenyl-4-methyl-1-pentene.

<Examples of other vinyl compounds>
Vinyl acetate, vinyl monochloroacetate, vinyl benzoate, vinyl pivalate, vinyl butyrate, vinyl laurate, divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl 2-ethylhexanoate, N-vinylcarbazole, N-vinylpyrrolidone etc.

  Said radically polymerizable compound can be easily obtained as a commercial product of the manufacturer shown below. For example, “Light acrylate”, “Light ester”, “Epoxy ester”, “Urethane acrylate” and “Highly functional oligomer” series manufactured by Kyoeisha Yushi Chemical Co., Ltd. “NK Ester” and “NK” manufactured by Shin-Nakamura Chemical Co., Ltd. “Oligo” series, “Fancrill” series manufactured by Hitachi Chemical Co., Ltd., “Aronix M” series manufactured by Toagosei Co., Ltd., “Functional Monomer” series manufactured by Daihachi Chemical Industry Co., Ltd. “ “Special acrylic monomer” series, “Acrylic ester” and “Diabeam oligomer” series manufactured by Mitsubishi Rayon Co., Ltd., “Kayarad” and “Kayamar” series manufactured by Nippon Kayaku Co., Ltd., “Acrylic acid / methacrylic acid ester” manufactured by Nippon Shokubai Co., Ltd. "Monomer" series, "NICHIGO-UV Purple Urethane Urethane" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Li Rate oligomer "series, manufactured by Shin-Etsu vinyl Co. acetate" carboxylic acid vinyl ester monomer "series, Kojin Co., Ltd." functional monomer "series, and the like. The radically polymerizable compound of the present invention may be used alone or in a mixture of two or more at any ratio in order to improve desired properties.

  A known compound can be used as the maleimide derivative. For example, JP 61-250064, JP 62-64813, JP 62-79243, JP 6-298817, JP 11-124403, JP 11-292874, JP 11-11 -302278, JP 2000-264922, "Polymer Materials Science and Engineering" Vol. 72, 470-472 (1995), "Polymer Preprints" Vol. 37, 348-349 (1996), “4th Fusion UV Technology Seminar”, pages 43-77 (1996), “Polymer Letters”, Volume 6, pages 883-888 (1998), “9th Fusion UV Technology Seminar”, 5-20 Page (2001) etc. You can use.

  Examples of the photopolymerization initiator that can be used in the present invention include all known photoacid generators.

  As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187. To page 192). Examples of compounds suitable for the present invention are listed below.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ and CF ₃ SO ₃ ⁻ salts of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium and phosphonium are listed. I can do it.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated substances that generate sulfonic acid can be mentioned, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

  The ink according to the present invention includes, for the first time, JP-A-8-248561 and JP-A-9-34106, and an acid proliferating agent that newly generates an acid by an acid generated by actinic ray irradiation that has already been known. It is preferable to do. The use of an acid multiplication agent is preferable because it can improve ejection stability and reduce curling and wrinkling of the recording material.

  The color ink according to the present invention contains various known dyes or pigments together with the above-mentioned actinic ray curable compositions, but preferably contains pigments.

  The pigments that can be preferably used in the present invention are listed below, but the present invention is not limited thereto.

C. I Pigment Yellow-1, 3, 12, 13, 14, 17, 81, 83, 87, 95, 109, 42,
C. I Pigment Orange-16, 36, 38,
C. I Pigment Red-5, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 144, 146, 185, 101,
C. I Pigment Violet-19, 23,
C. I Pigment Blue-15: 1, 15: 3, 15: 4, 18, 60, 27, 29,
C. I Pigment Green-7, 36,
C. I Pigment White-6, 18, 21,
C. I Pigment Black-7,
In the ink of the present invention, the colorant concentration is preferably 1 to 10% by mass of the whole ink.

  If necessary, other components can be added to the ink according to the present invention.

  When UV light, visible light, or infrared light is used as the radiation source, it is common to add a radical polymerization initiator, an initiator aid, and a sensitizing dye corresponding to each wavelength. These amounts usually require 1 to 10 parts by mass of the total ink. As the initiator and the like, various known compounds can be used, but the initiator is selected from those that dissolve in the polymerizable compound. Specific examples of the initiator include xanthone or thiooxanthone series, benzophenone series, quinone series, and phosphine oxide series.

  Moreover, in order to improve preservability, 200-20000 ppm of polymerization inhibitors can be added. The ink of the present invention is preferably heated and reduced in viscosity in the range of 40 to 80 ° C. and ejected. Therefore, it is preferable to add a polymerization inhibitor in order to prevent head clogging due to thermal polymerization.

  In addition to this, surfactants, leveling additives, matting agents, polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes are added to adjust film properties as necessary. I can do it. In order to improve adhesion to recording media such as olefin and PET, it is preferable to include a tackifier that does not inhibit polymerization.

  Specifically, a high-molecular-weight adhesive polymer ((meth) acrylic acid and an alcohol having an alkyl group having 1 to 20 carbon atoms, described on pages 5 to 6 of JP-A-2001-49200). Esters, copolymers of (meth) acrylic acid and C3-14 alicyclic alcohols, copolymers of (meth) acrylic acid and C6-14 aromatic alcohols), polymerization Low molecular weight tackifying resin having a polymerizable unsaturated bond.

  In order to improve the adhesion to the recording medium, an extremely small amount of an organic solvent that does not affect the drying property may be added. In this case, it is effective to add in a range that does not cause the problem of solvent resistance and VOC, and the amount is 0.1 to 5% by mass, preferably 0.1 to 3% by mass.

  Further, due to the light shielding effect of the ink coloring material, as a means for preventing a decrease in sensitivity, it is also possible to combine a cationically polymerizable monomer having a long initiator lifetime with an initiator to obtain a radical-cation hybrid curable ink.

  It is preferable to determine the composition ratio so that the viscosity of the ink composition is 10 to 500 mPa · s at 30 ° C. and 7 to 30 mPa · s by heating to 40 ° C. or higher (upper limit is about 50 ° C.).

  The reason is that by increasing the viscosity at room temperature, the ink can be prevented from penetrating into the absorbent recording medium, the uncured monomer can be reduced, the odor can be reduced, and dot bleeding at the time of landing can be suppressed. Image quality is improved. Further, since similar dots are formed between substrates having different surface tensions, similar image quality can be obtained. If it is less than 10 mPa · s, the effect of preventing bleeding is small. If it is higher than 500 mPa · s, there will be a problem in the supply of the ink liquid.

  In addition, in order to obtain stable emission properties, it is preferable that the viscosity of the ink composition at 40 ° C. or higher is 7 to 30 mPa · s.

  As recording materials that can be used in the present invention, in addition to ordinary uncoated paper, coated paper, and the like, various non-absorbable plastics and films used for so-called soft packaging can be used. For example, polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, triacetyl cellulose (TAC) ) A film can be mentioned. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used. Moreover, it is applicable also to metals and glass.

  The surface energy of these various plastic films varies greatly depending on the characteristics of the material, and it has conventionally been a problem that the dot diameter after ink landing varies depending on the recording material. With the configuration of the present invention, a good high-definition image can be formed on a wide range of recording materials having a surface energy of 35 to 60 mN / m, including OPP films having a low surface energy, OPS films, and PET having a relatively large surface energy. .

  In the present invention, it is more advantageous to use a long (web) recording material in terms of the cost of the recording material such as packaging cost and production cost, the production efficiency of the print, and the ability to cope with printing of various sizes. is there.

  Next, the image forming method of the present invention will be described.

  As described above, the image forming method using the ink set of the present invention is characterized in that white ink is ejected onto an image area formed of color ink and density correction is performed.

(Total ink film thickness after ink landing)
In the present invention, the total ink film thickness after ink has landed on the recording material and cured by irradiation with actinic rays is not particularly limited, and can be appropriately changed depending on the type of the recording material. In the actinic ray curable inkjet recording in the screen printing field, the total ink film thickness may exceed 20 μm, and in the flexible packaging printing field where the recording material is often a thin plastic material, it is preferably 2 to 20 μm. In addition to the problem of curling and wrinkling of the recording material, there is a problem in that the entire printed matter is changed in its strain and texture.

  Here, “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the recording material, and even for a single color, other two colors are superimposed (secondary color), three colors are superimposed, four colors are used. Even when recording is performed by the overlapping (white ink base) inkjet recording method, the meaning of the total ink film thickness is the same.

(Ink ejection conditions)
As the ink ejection conditions, it is preferable from the viewpoint of ejection stability that the recording head and ink are heated to 35 to 100 ° C. and ejected. Actinic radiation curable ink has a large viscosity fluctuation range due to temperature fluctuations, and the viscosity fluctuations directly affect the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  Moreover, in this invention, it is preferable that the amount of droplets discharged from each nozzle is 2 to 15 pl. Originally, in order to form a high-definition image, it is necessary for the amount of droplets to be within this range, but when discharging with this amount of droplets, the above-described discharge stability becomes particularly severe. According to the present invention, even when ejection is performed with a small droplet amount such as 2 to 15 pl, the ejection stability is improved and a high-definition image can be stably formed.

(Light irradiation conditions after ink landing)
In the image forming method of the present invention, the active light is preferably irradiated for 0.001 second to 2.0 seconds after landing of the ink, more preferably 0.001 second to 1 as the active light irradiation condition. 0.0 seconds, more preferably 0.001 to 0.5 seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

  As a method for irradiating actinic rays, the basic method is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method of the present invention.

  In addition, irradiation with actinic rays is divided into two stages. First, actinic rays are irradiated by the above-described method within 0.001 to 2.0 seconds after ink landing, and further, actinic rays are irradiated after all printing is completed. The method is also a preferred embodiment. By dividing the irradiation of actinic rays into two stages, it is possible to further suppress the shrinkage of the recording material that occurs during ink curing.

  Conventionally, in the UV ink jet system, a light source with high illuminance in which the total power consumption of the light source exceeds 1 kW · hr is usually used in order to suppress dot spreading and bleeding after ink landing. However, when these light sources are used, particularly in printing on a shrink label or the like, the shrinkage of the recording material is so large that it cannot be used practically.

  In the present invention, it is preferable to use an actinic ray having a maximum illuminance in a wavelength region of 254 nm, and a high-definition image can be formed even when a light source having a total power consumption of 1 kW · hr or more is used, and the recording material shrinks. Is also within a practically acceptable level.

  In the present invention, it is preferable that the total power consumption of the light source for irradiating actinic rays is less than 1 kW · hr. Examples of the light source having a total power consumption of less than 1 kW · hr include, but are not limited to, a fluorescent tube, a cold cathode tube, a hot cathode tube, and an LED.

  Next, an ink jet recording apparatus (hereinafter simply referred to as a recording apparatus) that can be used in the present invention will be described.

  Hereinafter, a recording apparatus according to the present invention will be described with reference to the drawings as appropriate. Note that the recording apparatus shown in the drawings is only one aspect of the recording apparatus that can be used in the present invention, and the recording apparatus according to the present invention is not limited to this drawing.

  FIG. 1 is a front view showing a configuration of a main part of a recording apparatus according to the present invention. The recording apparatus 1 includes a head carriage 2, a colored ink recording head 3, an irradiation unit 4, a platen unit 5, a white ink recording head 8, a scanner unit 9, and the like. In the recording apparatus 1, the platen unit 5 is installed under the recording material P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the recording material P. As a result, a high-definition image can be reproduced very stably.

  The recording material P is guided by the guide member 6 and moves from the near side to the far side in FIG. 1 by the operation of the conveying means (not shown). The head scanning means (not shown) scans the colored ink recording head 3 and the white ink recording head 8 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.

  The head carriage 2 is installed on the upper side of the recording material P. Depending on the number of colors used for image printing on the recording material P, a plurality of colored ink recording heads 3, which will be described later, and at least one white ink recording head are provided. Place and store on the lower side. The head carriage 2 is installed with respect to the main body of the recording apparatus 1 in such a manner that it can reciprocate in the Y direction in FIG. 1, and reciprocates in the Y direction in FIG. 1 by driving the head scanning means.

  In FIG. 1, the head carriage 2 includes a yellow (Y), magenta (M), cyan (C), and black (K) colored ink recording head 3 and a white (W: white ink) white ink recording head 8. Although drawing is performed for storage, the number of colors of the recording heads 3 and 8 stored in the head carriage 2 can be determined as appropriate.

  The recording heads 3 and 8 are operated by a discharge means (not shown) provided with a plurality of actinic ray curable inks (for example, UV curable ink) supplied by an ink supply means (not shown). The ink is discharged from the discharge port toward the recording material P. The UV ink ejected by the recording heads 3 and 8 is composed of a coloring material, a polymerizable monomer, an initiator, and the like, and the monomer crosslinks when the initiator acts as a catalyst when irradiated with ultraviolet rays. , Has a property of curing by polymerization reaction

  The recording heads 3 and 8 are located on a computer (not shown) during a scan in which the recording heads P are moved from one end of the recording material P to the other end of the recording material P in the Y direction in FIG. In order to reproduce the image data, UV ink is ejected as an ink droplet onto a certain region (landing possible region) in the recording material P, and the ink droplet is landed on the landing possible region. Further, the obtained image is read by the scanner unit 9 and the density difference from the original image data is calculated by the computer. If the image density needs to be corrected, the correction data is sent to the white ink recording head. An amount of white ink necessary for correction is overprinted on the image.

  The above scanning is performed as many times as necessary, and after UV ink is ejected toward one landable area, the recording material P is appropriately moved from the front to the back in FIG. 1, the recording heads 3 and 8 discharge UV ink to the next landable area adjacent to the rearward direction in FIG.

  By repeating the above-described operation and ejecting UV ink from the recording heads 3 and 8 in conjunction with the head scanning unit and the conveying unit, an image composed of an aggregate of UV ink droplets is formed on the recording material P.

  At this time, it is preferable to inject the color ink and the white ink as described above, eject the color ink as described above, read the image data with the scanner unit 9, and then eject the white ink onto the printing unit. At this time, a time difference is set so that the color ink and the white ink are not mixed, or after the color ink is ejected and actinic light is irradiated and cured, the white ink is ejected to the printing portion, and then the actinic light is emitted. It may be cured by irradiation.

  The irradiation unit 4 includes an ultraviolet lamp that emits ultraviolet light in a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet light of a specific wavelength. Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a cold cathode tube, a hot cathode tube, a black light, an LED (light emitting diode) and the like can be applied. A cathode tube, a hot cathode tube, a mercury lamp or black light is preferred. In particular, a low-pressure mercury lamp, a hot cathode tube, a cold cathode tube, and a germicidal lamp that emit ultraviolet rays having a wavelength of 254 nm are preferable because they can prevent bleeding and efficiently control the dot diameter. By using black light as the radiation source of the irradiation means 4, the irradiation means 4 for curing the UV ink can be produced at low cost.

  The irradiating means 4 is substantially the same as the maximum one that can be set by the recording apparatus (UV inkjet printer) 1 among the landable areas in which the recording heads 3 and 8 eject UV ink by a single scan driven by the head scanning means. It has a shape that is larger than the landable area.

  The irradiation means 4 is fixed on both sides of the head carriage 2 so as to be substantially parallel to the recording material P.

  As described above, as a means for adjusting the illuminance of the ink discharge portion, not only the entire recording heads 3 and 8 are shielded, but in addition, when the distance between the irradiation means 4 and the recording material P is h1, recording is performed. Increase the distance (h2) between the ink ejection part 31 of the head 3 and the recording material P (h1 <h2), or increase the distance (d) between the recording head 3 and the irradiation means 4 (d is increased). Is effective. Further, it is more preferable that a bellows structure 7 is provided between the recording head 3 and the irradiation means 4.

  Here, the wavelength of the ultraviolet rays irradiated by the irradiation means 4 can be changed as appropriate by exchanging the ultraviolet lamp or filter provided in the irradiation means 4.

  The ink of the present invention has excellent ejection stability and is particularly effective when an image is formed using a line head type recording apparatus.

  FIG. 2 is a top view illustrating another example of the configuration of the main part of the ink jet recording apparatus.

  The ink jet recording apparatus shown in FIG. 2 is called a line head system, and a plurality of ink jet recording heads 3 of each color are fixedly arranged on the head carriage 2 so as to cover the entire width of the recording material P. ing. Further, an ink jet recording head loaded with white ink is disposed on the head carriage 8.

  On the other hand, on the downstream side of the head carriage 2, there is provided irradiation means 4 arranged so as to cover the entire width of the recording material P and cover the entire area of the ink printing surface. As the ultraviolet lamp used for the illuminating means 4, the same one as described in FIG. 1 can be used.

  Further, a scanner unit 9 for reading image data is arranged between the head carriage 2 and the head carriage 8, and the image data information obtained as described above is sent to the computer.

  In this line head system, the head carriages 2 and 8 and the irradiating means 4 are fixed, and only the recording material P is conveyed, and ink ejection and curing are performed to form an image. The color ink and the white ink are ejected by the method described above.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Preparation of color ink>
According to the following method, the four color inks shown in Table 1 were prepared.

  Each color ink was prepared by adding 5 parts by mass of a dispersant (PB822 manufactured by Ajinomoto Fine Techno Co., Ltd.), each photopolymerizable compound (OXT-221, RSOX, Vikoflex 7010), a fluorine-based nonionic surfactant (Megafac F475, Mega FAC EXP.TF907) was placed in a stainless beaker and stirred and mixed for 1 hour while heating on a hot plate at 65 ° C. to dissolve. Next, after adding each colorant described in Table 1 to this solution, it was sealed in a plastic bottle together with 200 g of zirconia beads having a diameter of 1 mm, and subjected to a dispersion treatment for 2 hours in a paint shaker. Next, the zirconia beads are removed, a photo radical generator (Irgacure 651) and a photo acid generator (Chivacure 9000) are added, and this is filtered through a 0.8 μm membrane filter to prevent printer clogging, and the black ink (K) Cyan ink (C), magenta ink (M), and yellow ink (Y) were prepared. The viscosity of each color ink prepared above was in the range of 36 to 38 mPa · s.

<Preparation of white ink>
(Preparation of white pigment dispersion)
The following compositions were blended with a pressure kneader, and then kneaded and dispersed with a roll mill to obtain a white pigment dispersion.

Titanium oxide (average particle size 0.20 μm, refractive index 2.52) 25.00 parts by weight Neutral polymer dispersant 1.25 parts by weight Oxetane compound (OXT-221: manufactured by Toagosei Co., Ltd.) 73.75 parts by weight (Preparation of white ink)
The composition was mixed in the same manner as in the preparation of the color ink described in Table 1 and then filtered through a filter having an absolute filtration accuracy of 2 μm to obtain an actinic ray curable white ink.

<< Inkjet image formation >>
Each ink set composed of the color ink (4 colors) and white ink prepared above is loaded into 10 inkjet recording apparatuses (recording apparatuses 1 to 10) having the piezo-type inkjet nozzle and having the line head system shown in FIG. Then, based on original image data on a computer (not shown), Y, M, C, and K inks are ejected onto high-quality paper, cast-coated paper, and PET film to form an inkjet image, and irradiation means 4 The ink image was cured by irradiating with ultraviolet rays. Next, the image data obtained by the scanner unit 9 is read, image information is sent to the computer, the density difference from the original image data is calculated, and if the formed inkjet image density is higher than the original image density, the computer Correction data for ejecting white ink in an amount corresponding to the density difference was sent to the color ink printing section to perform density correction. Further, the irradiation unit 4 was irradiated with ultraviolet rays to cure the ink image. This series of operations was performed continuously.

The ink supply system was composed of an ink tank, a supply pipe, a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head. The ink was insulated from the front chamber tank to the head portion and heated at 50 ° C. The piezo head was driven so that 2 to 15 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi, and each ink was ejected continuously. After each color ink has landed, the irradiation light source (high pressure mercury lamp VZero085, manufactured by INTEGRATION TECHNOLOGY, peak wavelength: 254 nm, maximum illuminance: 400 mW / The ink was cured by irradiating with ultraviolet rays using cm ² ). After landing the white ink, the ink was cured by irradiating with ultraviolet rays in the same manner, but when observed after image recording, the color ink and the white ink were not mixed. Moreover, when the total ink film thickness was measured, it was the range of 2.3-13 micrometers. In the present invention, dpi represents the number of dots per 2.54 cm.

  Table 2 shows the concentration measurement results of the recording apparatuses 1 to 10 obtained as described above. Further, a sample on which an inkjet image was formed without using white ink (without correction) was compared, and the results are shown in Table 3.

  For each sample, the high density part and medium density part of each image of Y, M, C, and K were measured with a X-Rite 508 type densitometer (manufactured by X-Rite Co., Ltd.) and white paper on the back to measure the reflection density.

  From Tables 2 and 3, it is clear that when the density correction is performed with the white ink according to the present invention, the density variation between the printing apparatuses is significantly reduced for comparison.

  It was also found that the effects of the present invention can be reproduced even when the recording medium is different.

It is a front view which shows an example of a structure of the principal part of the inkjet recording device which can be used by this invention. It is a top view which shows another example of a structure of the principal part of the inkjet recording device which can be used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Head carriage 3 Inkjet recording head 31 Ink ejection port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure 8 White ink recording head 9 Scanner part P Recording material

Claims (6)

In an inkjet image forming method in which an image is formed with a first ink containing a color material, and then the image is corrected with a second ink containing a white pigment, the first ink and the second ink are not mixed. A method for forming an inkjet image. The inkjet image forming method according to claim 1, wherein the transmittance of the second ink image portion is 80% or less. The inkjet image forming method according to claim 1, wherein the second ink is an actinic ray curable white ink. It has a first inkjet head that ejects at least one yellow, magenta, cyan, and black ink, and a second inkjet head that ejects white ink, and the second inkjet head is an image by the first inkjet head. An inkjet image forming apparatus arranged to form an image after formation. The inkjet image forming method according to claim 1, wherein the apparatus according to claim 4 is used. A proof image forming method using the ink jet image forming method according to claim 1.

Images